MFC r350098, r350100-r350101

r350098:
Use ANSI C function definitions and declerations.

r350100:
Use headers instead of manual declerations of standard functions and
variables.

r350101:
Remove a duplicate global (rfc931_timeout).

It is declared here and in rfc931.c and unused here so keep that copy
and discard this one.

Obtained from: CheriBSD
Sponsored by: DARPA, AFRL